1. Field of the Invention
This invention relates to improvements in butterfly valves and more particularly, but not by way of limitation, to an improved adjustable seat for butterfly valves.
2. Description of the Prior Art
The usual butterfly valve comprises a valve body having a circular bore with a substantially disc-shaped closure member rotatably disposed therein. A pair of oppositely disposed shafts are normally provided on the closure disc and extend radially outwardly therefrom through suitable bosses, or the like, whereby the closure disc may be rotated about the axes of the shafts. Suitable valve sealing means and valves seating means is usually provided in the valve for precluding leakage of the fluid through the valve in the closed position of the disc. The sealing of the valves is extremely important, of course, and the sealing of the closure member in extremely large butterfly valves is frequently difficult. In order to improve the sealing of this type valves, adjustable seat members have been developed whereby sealing of selected portions of the outer periphery of the closure member may be provided to improve the overall sealing of the valve. Adjustable seat members of this type are shown in the I. M. White U.S. Pat. No. 3,144,040, issued Aug. 11, 1964, and entitled "Butterfly Valve", and the D. G. Fawkes U.S. Pat. No. 3,393,697, issued July 23, 1968, and entitled "Valve Seat". However, there is always a need for an improved manner of effecting an efficient seat and sealing for the butterfly valve disc.